Topic: Electric commuter car design

[piersdad]

Electric commuter car design

an encyclopedia on battery's here  http://www.mpoweruk.com/index.htm
a must look for anyone interested in EVs 
As I watch the huge number of new designs come out I wonder if they have actually lost the plot.
Artistic, streamlined, fast, slow, and darn site ugly etc none really practical as a mass commuter car.
If we look at the race car of  100 years ago and look at what they have today.

It is obvious today that fat tires, space frames, and totally enclosed passenger space were the way to go, but not 100 years ago.

So what do we want today in a dedicated commuter car that needs only get to the city speed limit of 50 km to 60 km/h  and 2 people to the 60 km daily commute.
It need not be the family car as it would only be used by the worker of the family and the other car can be any that suits the family situation.

1   It has to be safe and with the racecars they have what I call deflection safety where components like wheels etc are sacrificed to protect the driver.
VW had this with a solid metal central frame and it tended in a head on crash to push the car to one side allowing the mudguard and wheel to deflect the crash.
  I have not seen a VW with a direct head on crunch. Always a sideswipe.

So the chassis of an electric car has to have substantial beams or construction in the front that allows approaching solid objects to deflect the cars front from the passengers.
In the 1970s a research team used foam filled alloy box or shapes as part of a car and tested them to destruction.
The result was a huge amount of energy adsorption for the weight and size of the foam filled light alloy components.
An ideal aerodynamic front for any car which becomes a bumper as well.

The battery box then would be the main object to have in front
( batteries are cheaper,  can be insured, but  dead humans are difficult to replace)

 So  a solid battery box with a foam filled impact streamlining front nose cone.

This should not be fiberglass as this is both heavy and brittle  so at least a alloy  foam filled box . The alloy having crunching energy adsorbing ability.
Behind the battery is the passenger’s compartment.
Now who wants to crawl down to the level of a snake and wriggle into a super slim car?
No we need to approach the car and lift a gull wing door that enables one to walk into the car with dignity even with a child or carry cot in arms.
     The next  thing is the holding of the passenger in place by the seat belts.
These should have a attachment that has some limited give so that the passenger in a crash is decelerated slower than the car.
The car will be a total mess after a crash but the passengers are more important

These are the obvious things in their design and to date only one, near impossible to make , design has a walk in door.
All seem to be artistic and good looking or practical and darned ugly.

My own design from 1978 has all the features  I mentioned.
Is made from 3 sheets of alloy
And tubular frame
It is pleasant to look at but the  design could be better looking with combinations of different materials.
Alloy where best used.
Fiberglass where prettiness is needed.
Steel or alloy box section or tube where strength is needed.
 So here is my original design

click om image to enlarge

another pic with son inside befor we dumped it to stop the design falling into wrong hands
big mistake as it would now be in a musem


And here is the sketch of the newer chassis we never got to produce as we  went on then to make an electric truck and  all the buyers wanted a 2 seat electric commuter
Oh well we all make mistakes
.

click om image to enlarge


this is an approximate  drawing of the layout of the production car chassis
not a very good drawing as made from memory of 30 years ago but the general layout is shown

The use of a foam filled front and the batteries behind it  meant most of the cars weight was in front of the passengers and adsorbed a crash energy
so with a air bag system in a modern  version there would be a viable car suitable for today’s traffic

 

[piersdad]

Petrol cars are designed to do 100 plus km/h an area where EVs are at a disadvantage so the huge crash protection is not needed .
The EV should be designed for the suburban  environment  and leave the open highways for the fossil fueled cars.
The electric car  needs not to follow the very complicated  chassis of the modern petrol car but go more for the aero plane design. 
The use of rivets alloy, tubular frames  etc makes crash adsorption just as good as the modern heavy steel chassis.
The lighter weight means less energy in a crash has to be taken by the body.
As well the principle of deflection   from the impact site is also a good design idea.  Have you ever seen a VW car with full frontal impact damage, this is because the design tends to deflect the incoming to one side or the other.
A similar system with the batteries in the front (they are insurable) and passengers etc in the rear  so that an impact from most parts deflects the passenger compartment away due to the larger weight of the batteries.
A suburban EV does not have to have all the bit the present cars have like power steering and even power brakes as they need not exceed the local speed limit of 50 k
The result could be a lighter safer  efficient car for domestic runs like kids to school and shopping leaving the petrol car in the garage for the odd long distance drive or even to hire one for that special holiday or outing

[piersdad]

  battery managements systems
friend of mine said his laptop had a wireless BMS  which registered cell condition as well as charges /discharges.
my own experiences with life po4 batteries is that the customer must have security.
so a BMS that will not only tell you of a bad cell but also do some thing to protect the cell.
i have an old electric bike and the BMS shuts off the battery if a cell is down -- not a nice thing.
i went to my daughters chemistry lecture about battery chemistry and the  words  said " the anions and cations when combined in a solution form an inert substance" eureka??
is this the similar effect when the  lifepo4 battery gets below 2.7 volts and if tihs explanation is true or similar then make this clear to others as it explains why it is very important .
thus when a battery BMS says "help one cell is down" then the customer understands and takes urgent attention.
so instead of going to the petrol mechanic and getting a new fan belt you got to a electrician and get a replacement cell.
so a BMS that tells the mother  on her way to drop the kids of to school the BMS flashes a warning on the screen that says  'cell no 43 is sick please check it at --compliments abc beta batteries .co'--
this is possible now days.
my own experience on selling electric trucks in 1980 was  the continuous maintenance of the water levels and testing of the batteries was a  factor unsaid that lost us sales.

wow if back in the lead acid days of EVs if i had a BMS that said on a screen  cell no 23 needs water and cell group 5 requires replacement in 50 cycles approx
this would have given the owner assurance  that he will be able to budget a future cost  of running the battery/EV.
  So if a car was say 10 years old and for sale the seller/buyer would be able to view the BMS and come to a value left in the life of the battery.